A Schottky barrier device is a type of semiconductor device that utilizes the properties of a potential barrier formed between a metal-semiconductor junction to perform one or more functions. A typical Schottky barrier device may include a wide band-gap semiconductor layer, on which one or more metal contacts are placed to form a Schottky interface. Some exemplary Schottky barrier devices include Schottky diodes, high electron mobility transistors (HEMTs), and metal-semiconductor field-effect transistors (MESFETs). A HEMT incorporates a junction between one or more HEMT epilayers having a first band-gap and a semiconductor layer having a second band-gap (i.e., a heterojunction), at which a two-dimensional electron gas is formed, thereby creating a channel, which allows electrons to flow between a drain contact and a source contact. The potential barrier formed by a Schottky interface between a gate contact metal and the semiconductor layer is used to control the flow of electrons through the channel. Similarly, a MESFET uses a doped channel located in a semiconductor layer to allow electrons to flow between a drain contact and a source contact. Again, the potential barrier formed by a Schottky interface between a gate contact metal and the semiconductor layer is used to control the flow of electrons through the doped channel.
The geometry of the contact metal that forms the Schottky interface with the semiconductor layer may dictate several performance characteristics of the Schottky barrier device. For example, the speed of the Schottky barrier device may be directly related to the geometry of the contact metal. Generally, the smaller the area of the contact metal at the surface of the semiconductor layer where the Schottky interface is formed, the faster the Schottky barrier device can operate. Accordingly, many methods for forming contacts for a Schottky barrier device have focused on reducing the area of the contact metal at the surface of the semiconductor layer.
In addition to the geometry of the contact metal that forms the Schottky interface with the semiconductor layer, the distance between the source contact and the drain contact of a HEMT or MESFET may dictate additional performance characteristics of the Schottky barrier device. For example, the on resistance (RON) of the Schottky barrier device, as well as the turn on voltage (VON) of the Schottky barrier device, may be directly related to the distance between the source contact and the drain contact of the HEMT or MESFET. Accordingly, there is a need for Schottky barrier devices including precise contact geometries, and methods for manufacturing such devices.